The invention relates to an apparatus for testing the wheel suspension of a vehicle, comprising at least one measuring plate adapted to be moved by an excitation mechanism, a first measuring means for each measuring plate for measuring the vertical forces exerted by the air tire of the vehicle on the measuring plate, a processing unit for processing the measured values provided by the first measuring means and a display unit for displaying a measuring result.
While driving on a surface, vibrations are generated in the wheel suspension of a vehicle by the roughness of the surface. The most important vibration frequencies to which the wheel suspension of the vehicle is exposed during normal use on the road, lie in a range between 0 and 25 Hz. In this frequency range the wheel suspension generally shows two resonances, namely the resonance of the sprung mass (the body) lying between 0,7 and 2 Hz and the resonance of the unsprung mass (the wheel) lying between 10 and 15 Hz. The power density spectrum for usual speeds of the vehicle on the usual road surfaces shows a relatively high contents at low frequencies whereby the performance of the wheel suspension of the vehicle at low frequencies in particularly at the resonance frequency of the body, is of great importance.
In the known apparatus of the above-mentioned type conclusions are drawn from the course of the dynamic vertical force in the above-mentioned frequency range with respect to the operation of the shock absorbing element of the wheel suspension. The known apparatus however have the disadvantage that these conclusions are not always correct because the vertical force is also affected by other variables in the construction of the vehicle in addition to the shock absorbing element. For example the stiffness of the air tire has a great influence on the measuring results.
The invention aims to provide an improved apparatus of the above-mentioned type by means of which the wheel suspension of a vehicle can be evaluated with higher accuracy.